Chelsea made a dismal start to their Champions League campaign as Mislav Orsic guided Dinamo Zagreb to a shock 1-0 win over the disjointed Blues on Tuesday.
Orsic handed the hosts a surprise lead with a neat finish after racing onto Bruno Petkovic's flick-on just 13 minutes in, as Chelsea produced yet another toothless attacking display.
Chelsea debutant Pierre-Emerick Aubameyang struggled before being withdrawn on the hour, with Dinamo keeping Thomas Tuchel's men at arm's length with a superb defensive performance.
Having made a below-par start in the Premier League, Chelsea must now play catch-up in what could prove an awkward Champions League group, with games against Milan and Salzburg to come.
Chelsea should have gone ahead when Aubameyang failed to reach Kai Havertz's early cut-back, and paid the price when Dinamo hit the front shortly thereafter, as Orsic beat Wesley Fofana for pace before stabbing into the bottom-right corner.
Kepa Arrizabalaga saved well from Arijan Ademi's volley as Dinamo grew in confidence, and Chelsea recorded just one effort on target before half-time as the hosts defended in numbers.
Aubameyang was denied by the offside flag when he tapped Ben Chilwell's cut-back home five minutes after the break, before Chelsea were indebted to Kepa for tipping Stefan Ristovski's sweet strike onto the post.
Substitute Hakim Ziyech was unable to turn home an enticing right-wing cross as the visitors became more desperate, and Kalidou Koulibaly was perhaps fortunate to avoid a second booking for a foul on Petkovic.
Tuchel introduced Armando Broja and Christian Pulisic in search of a leveller, with Dominik Livakovic finally called into action with five minutes left, his reflex save denying Ziyech seconds after Reece James struck the right-hand post, as the Blues failed to find a way past the stubborn hosts on a chastening trip to Croatia.
What does it mean? Chelsea's blues continue
After a meek showing in Zagreb, Chelsea have suffered defeat in their opening Champions League match for just the third time in their 19 participations (W11 D5), also losing to Basel (2013-14) and Valencia (2019-20).
While Chelsea's ponderous attack has been criticised in the season's early weeks, they have also failed to keep a clean sheet in six outings across all competitions, their joint-longest such run since Tuchel took charge (also six in November-December 2021).
Orsic troubles English visitors
Orsic did brilliantly to bring down Petkovic's flick-on before his clever finish gave Dinamo a the lead, and he is beginning to carve out a reputation for tormenting Premier League sides.
He has scored five goals in his last four games against English teams in European competition (three v Tottenham, one v West Ham and Chelsea). Orsic is Dinamo's all-time top scorer in continental action with 18 goals (excluding qualifiers).
No fast start for Aubameyang
Tuchel backed Aubameyang to "prove a point" ahead of the trip to Zagreb, but the new arrival failed to record a shot on his first Blues outing, enjoying just three touches in the Dinamo area.
It was a far cry from Aubameyang's last Champions League appearance, when he scored a brace for Borussia Dortmund against Real Madrid in December 2017. While the former Barcelona man could yet solve Chelsea's attacking issues, he may need time to hit his stride.
What's next?
Chelsea go to Fulham for a London derby in the Premier League on Saturday. Dinamo, meanwhile, face HNK Gorica in the Prva HNL on the same day, before travelling to Milan in the Champions League next Wednesday.